Motor grader type construction machinery mount the motor grader blade or moldboard to a blade support frame. The blade support frame is rotatably mounted to a drawbar frame and typically includes a ring gear which engages a drive pinion of a motor mounted to the drawbar frame for rotating the blade relative to the drawbar frame and motor grader.
Prior motor grader assemblies mount the blade support frame to the drawbar using a number of shoe assemblies attached to the drawbar in a circular array and which support the blade support frame from the drawbar via the ring gear. Shims are used to set the individual clearances between the shoe assemblies and the drawbar. See for example U.S. Pat. No. 4,206,818.
Segmented ring gears are known for use with the combination swing gear and bearing for the slewing platform of a hydraulic excavator. For example, in U.S. Pat. No. 3,888,357, the combination swing gear and bearing comprises a plurality of gear segments detachably secured to one race member of the bearing assembly in a manner to form a continuous annular gear.
However, the blade support frame and ring gear of motor graders have heretofore been an integral assembly; that is, a one-piece ring gear attached to a blade support frame. As a result, when individual ring gear teeth break, for example due to shock loading of the blade, the entire blade support frame must be disassembled from the motor grader and the ring gear must be replaced. Reassembling the blade support frame to the drawbar requires reshimming of the ring gear relative to the shoe assemblies. Both the cost of the replacement ring gear and the cost in downtime of the machine result in significant repair expense for this procedure. This cost increases dramatically with the size of the motor grader, which for example can include blade lengths of up to 24 feet or more.
What is needed is a blade assembly for a motor grader which combines the ease of service found in the combination swing gear and bearing assembly of excavators with the simple blade mounting arrangement of current motor graders.